The present invention is related to a pleural or esophageal pressure predicting apparatus, a medical apparatus, a pleural or esophageal pressure predicting method, a diagnosing method and an examining method, which are capable of diagnosing a sleep apnea syndrome, an upper airway resistance syndrome, and the like, and also capable of evaluating a medical treatment effect, while monitoring, for instance, pleural or esophageal pressure conditions during sleep time.
Pleural pressure has close correlation with respect to health conditions of patients, and hence may be effectively used to diagnose closed type apnea syndromes and upper airway resistance syndromes and the like. However, it is practically difficult to measure such pleural pressure. Also, measurements of esophageal pressure which may substitute the above pleural pressure measurements cannot be easily carried out, since sensors should be inserted from nose holes into esophaguses which may give strong pain to patients. Therefore, in actual cases, the above sleep apnea syndromes and upper airway resistance syndromes are diagnosed by monitoring respiration conditions based upon air streams from noses, motion of breasts, motion of venter and the like.
However, in the case of such a diagnosing method by monitoring the respiration conditions based upon the air streams from the noses and the like, it is cumbersome to attach the sensors, or instruments. Furthermore, diagnostic precision of this respiration condition monitoring method is low. As a consequence, development of easier diagnosing methods with higher diagnostic precision has been strongly required in this medical field.
The present invention has an object to provide a pleural pressure predicting apparatus, a medical apparatus, a pleural pressure predicting method, a diagnosing method, and an examining method, capable of diagnosing a sleep apnea syndrome, an upper airway resistance syndrome, and the like, while pleural pressure can be predicted by way of a simple method without giving loads on patients.
According to the present invention, a pleural or esophageal pressure is predicted from pleural pressure based upon pulse wave signals, which are continuously produced and picked up in a time sequential manner. A first variation signal indicative of a condition of a variation (fluctuations of entire pulse wave signals) contained in the pulse wave signals is acquired based upon the pulse wave signals. A second variation signal representative of a condition of a variation (fluctuations of entire first variation signals) contained in the first variation signal is acquired based upon the first variation signal. The pleural pressure is predicted based on a difference between the first variation signal and the second variation signal.
This is based on a finding that there is a high correlation between a difference between the first variation signal (for example, first envelope) and the second variation signal (for instance, second envelope), and also the pleural pressure indicated by actual esophageal pressure.
The first variation signal shows a condition of variations (fluctuations) of the entire pulse wave signals in which a large number of pulse wave signals are continuously connected to each other. This first variation signal is mainly varied in response to a change contained in pleural pressure. Among signal components of this first variation signal, there are contained external disturbance components (for instance, signal components of autonomic nervous system for controlling blood pressure, for expanding blood vessel, and for compressing blood vessel) other than the pleural pressure.
The second variation signal corresponds to such a signal having a lower frequency (for example, lower than, or equal to 1 Hz) than the frequency of the first variation signal. Also, this second variation signal mainly contains the above external disturbance components. As a result, since the difference between the first variation signal and the second variation signal is calculated, such a signal indicative of only pleural pressure can be derived by eliminating the external disturbance components.